1. Field of the Invention
The present invention relates to a magnetic disk recording apparatus and, more particularly, to a magnetic disk recording apparatus that is compatible with disks whose storage capacities are respectively different.
2. Description of the Background
A data recording/reproducing apparatus for recording and reproducing digital data corresponding to a still picture to/from a magnetic disk having an outer diameter of around 2 inches has been known for some time. In addition, handy character processing apparatus using such a magnetic disk has been widely used.
Conventionally, such a magnetic disk has fifty circular tracks with a track pitch of 0.1 mm. The track numbers are inwardly assigned starting from outer track number 1 to inner track number 50, and the storage capacity per track is around 16 kilobytes. Thus, one disk can record data of around 819 kilobytes (16,384 bytes.times.50 tracks=819,200). In addition to the storage area for real data a disk usually has additional storage area for recording other information, such as preamble data, sync data, error correction data, ID data, and so on. This brings the storage capacity of a disk to around 1 mega-bytes. For this reason, the conventional magnetic disk having fifty tracks is hereinafter referred to as the 1M byte disk.
On the other hand, magnetic disks have been proposed where the number of tracks is increased in order to increase the storage capacity. For example, it has been proposed to add twenty tracks on both the outer and inner peripheries of the conventional fifty-track magnetic disk. Because the forty new tracks are added to the previously available fifty tracks, there is a total of ninety tracks. When there are ninety tracks, data of around 1.47 mega-bytes (16,384 bytes.times.90 tracks) can be recorded per disk. The disk having ninety tracks is hereinafter referred to as the 2M byte disk.
Specialized magnetic disk drive apparatus that can deal with the 2M byte disk has been developed, however, it is desirable that the same disk drive apparatus that deals with the new 2M byte disks should also be compatible with the conventional 1M byte disks. In other words, the magnetic disk drive apparatus that deals with the 2M byte disks should be capable of recording and reproducing data to/from the conventional 1M byte disks.